package com.lagou.sqlSession;

import com.lagou.pojo.Configuration;
import com.lagou.pojo.MappedStatement;

import java.lang.reflect.*;
import java.util.List;

public class DefaultSqlSession implements SqlSession {

    private Configuration configuration;

    public DefaultSqlSession(Configuration configuration) {
        this.configuration = configuration;
    }

    @Override
    public <E> List<E> selectList(String statementid, Object... params) throws Exception {

        //将要去完成对simpleExecutor里的query方法的调用
        SimpleExecutor simpleExecutor = new SimpleExecutor();
        MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementid);
        List<Object> list = simpleExecutor.query(configuration, mappedStatement, params);

        return (List<E>) list;
    }

    @Override
    public <T> T selectOne(String statementid, Object... params) throws Exception {
        List<Object> objects = selectList(statementid, params);
        if(objects.size()==1){
            return (T) objects.get(0);
        }else {
            throw new RuntimeException("查询结果为空或者返回结果过多");
        }
    }

    @Override
    public int insert(String statementid, Object... params) {
        return update(statementid,params);
    }

    @Override
    public int delete(String statementid, Object... params) {
        return update(statementid,params);
    }

    @Override
    public int update(String statementid, Object... params) {
        SimpleExecutor simpleExecutor = new SimpleExecutor();
        MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementid);
        try {
            return simpleExecutor.doUpdate(configuration, mappedStatement, params);
        }catch (Exception e) {
            throw new RuntimeException("sql执行异常:"+e.getMessage());
        }
    }



    @Override
    public <T> T getMapper(Class<?> mapperClass) {
        // 使用JDK动态代理来为Dao接口生成代理对象，并返回

        Object proxyInstance = Proxy.newProxyInstance(DefaultSqlSession.class.getClassLoader(), new Class[]{mapperClass}, new InvocationHandler() {
            @Override
            public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
                // 底层都还是去执行JDBC代码 //根据不同情况，来调用selctList或者selectOne
                // 准备参数 1：statmentid :sql语句的唯一标识：namespace.id= 接口全限定名.方法名
                // 方法名：findAll
                String methodName = method.getName();
                String className = method.getDeclaringClass().getName();

                String statementId = className+"."+methodName;

                Object result;
                switch (methodName) {
                    case "insert": {

                        // 执行 INSERT 操作
                        result = insert(statementId, args);
                        break;
                    }
                    case "update": {
                        result = update(statementId, args);
                        break;
                    }
                    case "delete": {

                        // 转换 rowCount
                        result =delete(statementId, args);
                        break;
                    }
                    case "select":
                        result= selectOne(statementId, args);
                        break;
                    case "selectAll" :
                        result = selectList(statementId, args);
                    default:
                        throw new IllegalStateException("Unexpected value: " + methodName);
                }

                return result;
            }
        });

        return (T) proxyInstance;
    }




}
